Magnetic transducers in contact with the recording medium exhibit wear in the transducer-to-medium interface area due to abrasion effected by the medium. Such wear shortens the useful life of the transducer, which has to be often replaced at considerable cost. Among the desirable features of magnetic transducers, in addition to wear resistance, is to have a well defined transducing gap which maintains its shape during the useful life of the transducer. To extend transducer life, while also improving transducing gap definition and integrity, various magnetic as well as nonmagnetic materials have been utilized in the transducer-to-medium interface area, in combination with magnetic core materials having desirable magnetic propertes. However, such known composite core structures are rather complex, and they employ complicated, and therefore costly manufacturing methods.
Magnetic materials which provide excellent gap definition and integrity generally have high granular density, and therefore are not susceptible to "pullouts" of small grains of material during the manufacturing process or operation. Such pullouts lead to chipping or breaking of the magnetic material, thereby damaging the sharp edges defining the transducing gap, and degrading the gap. Pullouts may occur during certain manufacturing steps, for example lapping, or during operation, when the transducer is in contact with the medium at high relative transducer-to-medium speed.
An example of a type of magnetic materials having high granular density and which are known to provide very good gap definition, while also having desirable wear resistance propertes, are single crystal ferrites. However, as it is well known, single crystal ferrite when utilized in magnetic transducers in contact with the medium exhibits a disturbing rubbing noise, which distorts the information signal. Rubbing noise is attributed to magnetostriction which, as well known is a property of a magnetic crystal material to change the magnetic reluctance in response to an external force. In this case the external force is represented by the magnetic medium in contact with the magnetic crystal material of the transducer. It is further known that when utilizing single crystal ferrite, the magnetic as well as other properties, such as rubbing noise, wear rate or material strength, each may be optimized by selecting a particular crystal axis orientation. However, when the crystal axis is oriented to optimize one parameter, for example to minimize rubbing noise, the other parameters will not be at their optimum values, and the overall transducer performance will suffer.
There are other magnetic materials with high granular density which provides a desirable gap definition, but they have other, less desirable properties when utilized in a large quantity in the magnetic transducer structure. Examples are metallic magnetic materials, such as Sendust or amorphous magnetic materials. These materials are known to provide excellent transducing gap definition and integrity, but they also have undesirable high frequency losses. Therefore, it is desirable to use only a minimum amount of these high density materials, in combination with other suitable magnetic materials, to reduce frequency losses.